Turbulent mixing in strongly stratified shear flows

Motivated by the importance of irreversible mixing in geophysical and environmental flows, we seek to understand the dependence of its efficiency under strongly stratified conditions through a seris of direct numerical simulation of Holmboe wave instability under various initial conditions. Our numerical findings demonstrate that while mixing is enhanced when the density layer is much sharper than the shear layer, it is weakened if the background density jump across the interface increases while the background shear remains fixed. Furthermore, our results suggest that mixing efficiency of energetically turbulent flows is likely not to ever be suppressed despite arbitrarily strong stratification at the interface of a Holmboe wave.